Infinitives: Who to, What to, etc...

1. Indirect Questions (Tell us what to do.)
Question words like who, what, where, etc. except why, infinitives can be used in indirect speech. This form usually expresses ideas of obligation and possibility.

Examples:
Tell me where to go.
I wonder who to call.
I don't know what to do next.
Tell me when to stop the cooking.
Can you show how to get to the hotel?
I'm confused whether to drive or take the train.

2. Direct Questions (What shall we do?)
Direct questions doesn't usually begin with How to...? What to...? Where to...? etc. Often, after the question words, shall and should are used.

Examples:
How shall I approach her?
What shall I bring with me?
Who should I ask for help?
Where shall we go from here?
When should we submit the project?

3. Titles
How to..., What to..., When to..., etc. are usually used in titles such as those found in instruction manuals, product leaflets, books, brochures. etc.

Examples:
HOW TO TRAVEL LIGHT
WHERE TO STORE YOUR VALUABLES
WHAT DO IF THERE'S AN EARTHQUAKE
WHO TO CALL DURING AN EMERGENCY
HOW TO IMPROVE YOUR COOKING SKILL